Ocean trench cruise finds brand new fish
15 October 2010, by Tom Marshall
An entirely new species of fish and a feeding frenzy of cusk-eels, in a place where – until now – nothing was thought to live, are among the highlights of a recent research expedition to the south-east Pacific.
An international team of marine biologists made these discoveries with a specially-designed unmanned lander, which sinks down to the seabed, attracts local animals with fish bait and photographs them with an automated camera.
The lightless depths several kilometres down were once thought to be devoid of life, but more recent research has found amazingly rich, complex and diverse ecosystems even at the bottom of the deepest ocean trenches.
New species of snailfish at 7000m
After previous voyages elsewhere in the Pacific, the researchers suspected each trench has its own unique kinds of snailfish that have evolved there in isolation. The latest results, from the little-explored Peru-Chile trench, lend support to that idea; the team caught a completely new species of snailfish on film seven kilometres down, as well as being surprised to see a swarm of cusk-eels at a depth where they didn't expect to find anything. The unprecedented feeding frenzy continued throughout the lander's 22-hour stay on the seabed.
'These are some fantastic results and will prompt a rethink into fish populations at extreme depths,' says team leader Dr Alan Jamieson of the University of Aberdeen's Oceanlab research centre. 'We'll be scratching our heads over this for a while; it's absolutely not what we were expecting. These results highlight the significance of the individual trench environment rather than simply depth itself'.
The team also found unexpectedly large examples of the Eurythenes subfamily of the group of crustaceans known as amphipods. The scientists are increasingly realising that each trench has a unique set of inhabitants.
'The sheer abundance of these big amphipods was overwhelming, particularly at 7000m and 8000m, which is much deeper than they have been found in any other trench' says Dr Niamh Kilgallen, an amphipod specialist at the National Institute of Water & Atmospheric Research (NIWA) in New Zealand who took part in the expedition. 'It begs the question of why and how they can live so deep in this trench but not in any other.'
Feeding frenzy of cusk-eels at 6000m
The expedition, aboard the German research ship Sonne, was the latest leg of the Hadeep project, a collaboration between the Universities of Aberdeen and Tokyo, with additional support from NIWA. It aims to uncover the mysteries of life in the Hadal zone, which stretches from six kilometres below the sea's surface down to the deepest parts of the ocean at the bottom of the great marine trenches.
The scientists surmise that because these trenches are so far from each other, each species has been able to develop in isolation, like the unique animals of the Galapagos that helped inspire Darwin's theory of evolution by natural selection.
The Hadeep project is funded by the Nippon Foundation in Japan and the UK's Natural Environment Research Council. Highlights of previous voyages include the deepest fishes ever caught on film – watch the footage using the links to the right.
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